What are the results of Zinc in your alloy?

[prickett]

I cast some .45's the other day and the allow had a bunch of oatmeal looking gunk floating on top. Somewhere in the back of my mind I remembered that could be zinc in my mix. I cast anyway and ended up with decent boolits. Upon shooting them, however, I ended up with SEVER leading - again this for .45 ACP. I've never had them lead. It has me wondering if zinc would cause leading. I'd think that zinc is harder, so it shouldn't. Anyone have any guesses?

[cbrick]

If that oatmeal looking stuff was silver looking its in all probability antimony and should be fluxed back into the melt. Sawdust is very good at reducing the antimony and tin.

Zinc would be a very dull color and if there was much in the alloy you wouldn't have "decent bullets".

Would zinc cause leading? Dunno, I do everything I can to keep it out of my alloy but I doubt it, just make lousy bullets.

Rick

[44man]

I had some get into pure lead once. My boolits looked like a rain gutter.
I just set the pot to barely melt and scooped it off.
I have never seen antimony form on the surface.

[prickett]

If that oatmeal looking stuff was silver looking its in all probability antimony and should be fluxed back into the melt. Sawdust is very good at reducing the antimony and tin.

Zinc would be a very dull color and if there was much in the alloy you wouldn't have "decent bullets".

Would zinc cause leading? Dunno, I do everything I can to keep it out of my alloy but I doubt it, just make lousy bullets.

Rick

I do/did stir with a wooden stick then put a blanket of sawdust on the surface, then cover the pot with a metal cover (made from an old license plate)

[XWrench3]

IF memory serves me right, and it may not, isn't zinc harder than lead? if so, i do not know how it could cause leading. also, i remember someone here actually made boolits from zinc, and they shot fine. i do not know how zinc acts as it cools. it may shrink more than lead does. and that may cause some leading, IF that is the case. i have not yet experieneced zinc in my lead. i keep a CAREFUL eye on the smelting pot, and never let it get hot enough for the zinc wheel weights to melt. that is the only way i have ever smelted, and it works fine for me. as far as oatmel looking stuff in a pot, the only time i have seen that is with linotype. i just turn the heat up a few notches, stir and flux until it mixes back into the alloy.

[cbrick]

1) Since the Zinc melts at a lower temperature than lead, Jeff

Say what? Huh?

Lead melts at 621 degrees.
Zinc melts 787 degrees.

I have never seen antimony form on the surface.

I have but only a couple of times. I "think" that it takes a slow heat up or some such circumstance. I have tried to recreate it to find out how/why it happened and didn’t succeed.

The first time I saw this I stirred and stirred and it remained. I sprinkled saw dust on top of it and as the sawdust started to burn most of it just disappeared, stirring the flux got rid of the rest. It was an amazing thing to see.

The slow heat up is a SWAG on my part based on the difference in melting temps of lead/antimony.

Rick

[44man]

Say what? Huh?

Lead melts at 621 degrees.
Zinc melts 787 degrees.



I have but only a couple of times. I "think" that it takes a slow heat up or some such circumstance. I have tried to recreate it to find out how/why it happened and didn’t succeed.

The first time I saw this I stirred and stirred and it remained. I sprinkled saw dust on top of it and as the sawdust started to burn most of it just disappeared, stirring the flux got rid of the rest. It was an amazing thing to see.

The slow heat up is a SWAG on my part based on the difference in melting temps of lead/antimony.

Rick

That is why zinc can be removed at the lead or alloy melt point. It makes a slush on the surface before heat gets too high and it melts in.

[fecmech]

In previous posts I have mentioned contaminating a couple smelts with zinc. The first is behind the garage but the second I tried to skim the zinc after lowering the temp and added 2% sn. I have since cast a lot of bullets with the mix and they cast fine and shoot as good as my ACWW+2%. I do not have a hardness tester but I test ingots with a ball bearing between a pure lead ingot and the unknown ingot.
My zinc'ed ingots test about 3 BHN higher than my ACWW and I'm assuming that holds for the bullets as well. YMMV

[GaryN]

"If the alloy is thick, and a bluish grey color, it is probably contaminated with Zinc."

Umm, I just melted down a bunch of monotype. It looked bluish gray and was kinda thick. I thought it was just the high antimony content.

[nighthunter]

I think it is just dirt in the alloy. Dirty alloy to me is the single biggest problem in casting. Most casting problems can be traced to either dirty alloy or temperature of the alloy. Flux your alloy and stir it in the pot with a hardwood wooden strip or dowel and you will be surprised at what will come out of the alloy. Rub that oatmeal like stuff against the side of the pot with the piece of wood. Rub it till all you have is a pile of dirt floating on top of the alloy. Now you are ready to cast bullets.

Nighthunter

[runfiverun]

antimony givess a greyish bubbly looking stuff.
you just need to turn up the heat and flux it in.
zinc is silver oatmeal.
zinc will mix into a lead alloy and tin does help it alloy better, but it works best if you keep it under 1.6-2% after that it tends to wreak havoc.
if you get a bunch of zinc into an alloy it will tend to strip your tin from the mix as you remove it.
there is a stcky here somewhere about using sulpher to remove zinc from a contaminated alloy at least enough to make it cuttable into a useable one.